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The cochlea — the chamber of the inner ear that takes its name from the Greek word for "snail shell" because of its shape — contains nerve endings that send electrical impulses to your brain. These impulses become the sounds you hear.

If you have severe damage to these nerve endings, a hearing aid may not be enough to overcome the degree of hearing loss you're experiencing. But an electronic device called a cochlear implant, which places electrodes deep within the cochlea to bypass these nerves, may be the answer for you.

People who could benefit from cochlear implants include children who are born deaf and adults who develop gradual deafness over time and don't benefit from hearing aids, explains Elizabeth H. Toh, MD, an ear, nose, and throat surgeon at the Lahey Clinic in Burlington, Mass. People with partial hearing loss or deafness in only one ear are not usually offered this type of treatment.

Cochlear Implants: How They Work and How They Look

On the outside, a cochlear implant looks like a behind-the-ear hearing aid, but it has both external and internal parts. Here is how a cochlear implant works:

A microphone worn behind the ear picks up sound just like a hearing aid.

A tiny computer, called a speech processor, "organizes" the sound and sends it to a transmitter, which is also worn behind the ear.

The external transmitter sends the sound signals to a receiver that has been implanted under the skin behind the ear.

This internal receiver sends the sound signals to electrodes that have been placed inside the cochlea to stimulate hearing nerves that go to the brain.

"Cochlear implants work best for adults who have recently lost their hearing," Dr. Toh says. "For these people, word recognition starts out sounding strange, but the brain adjusts quickly."

"For children who have never had hearing, cochlear implants work best when they are implanted at an early age," Toh says. "In some cases, children with early implant surgery can develop normal speech and can be indistinguishable from children with normal hearing."

How Cochlear Implants Are Performed

Cochlear implant surgery is done under general anesthesia and is very safe. The procedure can take up to two hours, and most people can go home on the same day, but the entire process will take several months. Four weeks after surgery, you will need to have the implant activated, and then you'll work with a hearing specialist for about six months to adjust the device.

Children who have never had speech and adults who have lost hearing for a long time may also need to work with a speech therapist. There is a lot of training that goes with a cochlear implant, and some people have more success than others. A cochlear implant won't fully restore normal hearing, but most people benefit significantly.

The Future of Cochlear Implants

According to recent figures, about 43,000 adults and 28,000 children in the United States have had a cochlear implant. Most insurance plans now cover the procedure in one ear. The technology that's involved in the implants is also improving, and the future looks bright for more people with more types of hearing loss.

Future developments may include:

Bilateral cochlear implants. Putting implants in both ears is recommended by many hearing specialists. "The battle is now over getting insurance companies to cover the second implant," Toh says.

Cochlear implants for the partially deaf. Researchers are learning how to place electrodes to restore hearing for people who have hearing loss only for high-frequency sounds.

Completely implanted cochlear implants. "In the future, there may no longer need to be any external parts to the implant," Toh says.

If you have severe deafness that's not helped by hearing aids, a cochlear implant can be a medical miracle. Ask your doctor to refer you to a cochlear implant center. For the right candidate, these electronic devices can often provide the gift of sound.

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